Harmonic generator



Oct. 25, 1927.

1,646,438 H. A. AFFEI; Y

HARMCNIC GENERATOR Filed May 15, 19,23 2 Sheets-Sheet 2 I N V15 N TO R Ja 7M 7 Patented Oct. 25, 1927.

UNITED STATES HERMAN A. AIIEL, OF BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE PATENT OFFICE.

AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

HARMONIC GENERATOR.

Application filed May 15,

This invention relates to high frequency generation and more particularly to the generation of high frequencies by means of harmonic producers.

In carrier signaling systems it has, to some extent, been the practice to generate the carrier frequencies for the different signaling channels by a process of harmonic generation. Heretofore, this method has been used, however, only with relatlvely low harmonics. It is possible, however, to obtain high harmonics by generating thehigh frequencies in a number of steps, that is, by generating first a relatively low harmon c in one distorting device, such as a vacuum tube, for example, and successively multiplying the frequency thus produced by passmg it through other tandem distortmg C11- cuits.

In accordance with the present invention it is proposed to attain this successive or cascade eneration of harmonics by means of a fee -back circuit so that only one distorting device or tube may be needed to effect the successive frequency transformations. It should be noted that a feed-back circuit of this type differs from the ordinary feed-back circuit in that a different frequency from the frequency orlgmally applied to the tube is led from the output to the in ut circuit so that no singing effect will resu t.

The invention may now be more fully understood from the following detailed description whenread in connection with the accompanying drawing, Figure 1 of wh ch is a simp ified circuit diagram illustrating one embodiment of the invention and Figures 2, 3 and 4 of which are circuit dia grams illustrating alternative embodiments of the invention.

Referring to Fig. 1, S denotes some suitable source of alternating current having a frequency f and V designates a vacuum tube device of well known type whose constants are so adjusted that it distorts the wave form of any electromotive force impressed thereon. The source S is coupled to the input circuit of the distorting tube V, through windings 10 and 11' of a transformer 13. The output circuit of the distorting tube is coupled to an outgoing circuit 0 1923. Serial No. 639,176.

through windings 14 and 15 of a transformer 17. A third winding 16 of the transformer 17 is inductively related to the windmg l4 and is connected in circuit with a plurallty of selecting circuits 18 and 19, each tuned to a desired harmonic frequency of the fundamental frequency generated by the source S.

The selecting circuits 18 and 19 are coupled to the input circuit of a vacuum tube distorting device V through windings 20 and 21 of a transformer 22. The vacuum tube device V is similar to the device V already described. The output circuit of the distorting tube V is coupled through windings 23 and 24 of a transformer 25 to another grou of select-in circuits 26 and 27, each tune to suitable armonics of the fundamental frequency f. These selectin circuits are coupled to the input circuit 0 the first distorting device-V through windmgs 11 and 12 of the transformer 13. It will thus be seen that a complete circular path for the transmission of energy at successive frequencies is provided.

The operation is as follows: The frequency f, impressed upon the input circuit of the dlstorting device V results in the production in the output circuit of said device of various harmonic frequencies of the fundamental frequency, among which the second harmonic 2 will be prominent. The second harmonic 2 will be transmitted directly to the outgoing circuit 0 and will also be transmitted through the winding 16 to the tuned circuit 18. The latter, by reason of its couplin to the input circuit of the distorting device V will transmit the frequency 2 to said distorting device so that the second harmonic of this frequency, or 4', will appear in the output circuit thereof. The frequency 4 will in turn be selected by the tuned circuit 26 and transmitted through the transformer 13 to the input circuit of the original distorting device V The latter will in turn produce in its on put circuit, the second harmonic frequency 8 of the frequency 4. The harmonic frequency 8 will be transmitted directly to the so that the second harmonic of the frequency 16, or a frequency 32, will be impressed upon the outgoing c1rcu 1t O.

In addition to the fre uencles already mentioned as being transmitted directly to the outgoing circuit 0, it is apparent that all of the fundamental frequencies impressed upon the input circuit of the vacuum tube V, will also appear in the output c rcult so that the frequencies f, 4 and 16 w ll be directly transmitted to the outgoing clrcult O in addition to the harmonics noted. Also it will be apparent that since the distorting tubes are, in effect, modulating devices, al of the frequencies impressed upon the distorting device V will modulate each other 7 to produce sum and difference frequencies as well as harmonics, and these sum and difference frequencies may be transmitted directly to the outgoing circuit 0. As a conse uence, practically any harmonic of the fun amental frequency 7 may be obtained in the outgoing circuit Q and, by prov ding suitable selective devices in the outgoing circuit 0, any desired harmonic may be segregated for any purpose desired.

It will be observed that the system above described provides for the recurrent transmission of energy through a circular path, the energy being translated in frequency at each successive stage of its transmlsslon through the path.

A modified arrangement for attaining the results above outlined is illustrated in Fig. 2. In this case, a balanced vacuumtube circuit involving the tubes V and V 1s employed, the circuit being of a well known type so arranged that the amplification component may be suppressed and the double frequencies transmitted. The alternating current source S is coupled to the input C11- cuitof the balanced vacuum tube arrangement through windings 30 and 31 of a transformer 32. The output circuit of the balanced vacuum tube arrangement is provided with a winding 34 of a transformer 35 in the common branch of said output circuit and the winding 34 is inductively related to a winding 36 associated with a series of tuned selecting circuits 38, 39 and 40, each tuned to particular harmonics of the fundamental frequency f. The tuned circuits 38, 39 and 40 are coupled to the input circuit of the balanced vacuum tube arrangement through the winding 33 inductively related to the winding 31 of the transformer 32. If desired, an additional tube V may be associated with the output circuit of the dis torting tube arrangement V V through a winding 37 inductively related to the winding 34. The tube V, may be utilized either to amplify frequencies transmitted thereto or to mo ulate together a plurality of freuencies transmitted thereto, thereby producing sum and difference frequencies of such individual frequencies.

The 0 eration is as follows: The fre uency f upon being impressed upon the istorting tubes V and V produces in the common output branch including the winding 34, even harmonics of the frequency f. The odd harmonics includin the fundamental f will be suppressed. The second harmonic 2 will be transmitted through the windings 34 and 36 to the tuned circuit 38 and in turn will be transmitted from the tuned circuit 38 through the windings 33 and 31 to the input circuit of the balanced distorting arrangement. This will result in the production of a frequency 4 in the output circuit, which will be selected by the tuned circuit 39 and impressed upon the input circuit of the distorting tubes V and The second harmonic (8) of this frequency will appear in the output and will be selected by circuit 40 to be applied to tubes V and V so that finally a frequencv 16 will be produced and transmitted through the windings 34 and 37 to the input circuit of the vacuum tube V The other frequencies generated in the winding 34 such, for example, as the frequencies 2, 4 and 8', will also be impressed upon the input circuit of the tube V If the tube V is adjusted to operate as an amplifier these frequencies will be amplified directly and may be selected individually into suitable circuits for any purpose desired. If, however, the tube V, be adjusted to operate as a modulator it will produce frequencies correspondingto the sums and differences between the several frequencies impressed upon its input circuit so that in the output circuit there will appear frequencies corresponding to these sums anddiflerences, as well as to the several harmonies already referred to.

It will be noted that by reason of the balanced arrangement of the vacuum tubes V and V no singing is possible as the fundamental frequency f is balanced out as regards the winding 34, which is included in the common branch of the output circuit.

It will also be noted that in the above circuit continuous oscillation or singing cannot take place at any frequency since an frequenc transmitted to the input circuit will be balanced out in the output circuit and not be transmitted back circuit.

A circuit arrangement such as that above described is peculiarly advantageous as it enables the production of any high frequency desired from a very low fundamental frequency. Thus, a tuning fork, for example, may be used to control the generation of a to the input low fundamental frequenc which will be very accurately determine and the corresponding harmonics of the fundamental frequency will be likewise accurately fixed with respect to frequency. A circuit arrangement illustratin this principle is shown in Fig. 3, in which tiie tuning fork F is magnetically associated with U-shaped cores 50 and 51, so that the tines of the fork form a path for the flux passing from one leg of the U to the other. The input winding 31 of a balanced distorting tube arrangement V V such as that illustrated in Fig. 2, is wound upon the core 50, while windings 52 and 53, included in the individual branches of the plate circuits of the balanced arrangement, are wound upon the core 51. A Winding 34, included in the common branch of the output circuit, is wound upon a core 54, having inductively associated therewith a winding 37 included in an outgoing circuit 0. The core 54 also includes windings 36, 36' and 36 associated with tuned circuits 38, 39 and 40. Each of the tuned circuits just referred to includes an individual winding upon the core 50, as indicated at 33, 33 and 33".

The operation is as follows: Assuming that the tuning fork F is set into vibration so that the tines of the fork vibrate alternately toward and away from each other at a frequency f, it is apparent that the vibration of the left-hand tine produces changes in the flux of the core 50, these changes in turn producing potential fluctuations of the same frequency upon the grids of the vacuum tubes V and V Since the vacuum tubes V and V are distorting devices, even and odd harmonics will be produced, the even harmonics flowing through the winding 34 and the odd harmonics being balanced therefrom, while the odd harmonics flow through the windings 52 and 53, the even harmonics being prevented from flowing through these windings by the balanced arrangement of the circuit. The fundamental frequency 7 will consequently appear in the windings 52 and 53, thereby producing changes in the flux inthe core 51 and causing thetines of the tuning fork F to vibrate in correspondence therewith. As a consequence, the tuning fork F, once set in vibration, continues to vibrate owing to the mechanical feed-back connection between the output and the input circuits through the cores 51 and 50 and the tuning fork F.

The second harmonic 2, flowing through the winding 34, will be transmitted through the windin 36 to the tuned circuit 38 and impressed t rough windings 33 and 31 upon the input circuit of the balanced distortlng device, thereby producing a frequency 4 in winding 34 of the output circuit. This frequency is in turn selected by the circuit 39 and impressed upon the input circuit to produce a frequency 8, which in its turn is also fed back to the input circuit, finally 'producing a frequency 16 in the winding 34.

As a consequence, the several even harmonic frequencies referred to will be transmitted through the coupling of windings 34 and 37 to the outgoing circuit 0 and may be utilzed in any desired manner.

Instead of using vacuum tube devices for distorting purposes, as illustrated in Fig. 2, any type of rectifying device may be used, as indicated at B and R, of Fig. 4. It will be noted that in this figure the winding 34 is included in a common branch of the balanced circuit arrangement so that only even harmonics will flow through this windmg and the fundamental or any other frequency impressed upon the winding 31 cannot be fed back to said winding through the transformer windings 34 and 36. The fundamental frequency f is generated by a mechanically operated tuning fork T, the tunin fork being actuated by a magnet M included in circuit with the winding 30 of transformer 32, a suitable source of current and an interrupting or resistance changing device B mechanically actuated by the tine of the tuning fork. The tuning fork is thus arranged to automatically control the energization of the magnet M so that its action w1l1 be contlnuous to supply a periodically varlable current to the winding 30.

The operation will, of course, be obvious. The rectifying devices R and R distort the frequency impressed upon the windin 31 to produce harmonics and the second armonic is selected by the tuned circuit 38 and impressed upon the input winding 31. The second harmonic of this frequency in turn appears 1n the output circuit and 1s selected by theclrcuit 39 and impressed upon the input winding 31. Finally, th'e. second harmomc of this frequency (8) is produced in the output circuit and selected by the circuit 40. The frequency 8 is then transmitted from the circuit 40 through the transformer 60 to the outgoing circuit 0.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations Widely different from those illustrated without departing from the spirit of the invention as defined'in the following claims.

What is claimed is:

1. A harmonic generator comprising a source of fundamental frequency, a static translating device upon which said fundamental frequency may be impressed, said static translating device having an input circuit and an output circuit and being adapted to produce harmonics of. the fundamental frequency, a reentrant connection from the output circuit of said translating device to its input circuit, said reentrant connection comprising a plurality of paths each adapted to feed back into the input circuit of said translatin device a different harmonic frequency pro uced in the output circuit thereof, thereby producing frequencies which are harmonics of the frequencies fed back, and means to prevent alternate harmonics from being fed back.

2. A harmonic generator comprlslng a source of fundamental frequency, a vacuum tube translating device upon which said fundamental frequency may be impressed, said vacuum tube translating device having an input circuit and an output circuit and being adapted to produce harmonics of the fundamental frequency, and a reentrant connection from the output circuit of said vacuum tube translating device to its input .circuit,said reentrant connection comprislng a plurality of paths each adapted to fee back into the input circuit of said vacuum tube translating device a different harmonic frequency produced in the output circuit thereof, thereby producing frequencies which are harmonics of the frequencies fed back,

and means to revent alternate harmonics from being fed ack. v

3. A harmonic generator comprising a source of fundamental frequenc a distorting device upon which said fundamental frequency may be impressed, said distorting evicehavin an input circuit and an output circuit and eing adapted to produce harmonies of said fundamental frequency, a reentrant circuit connecting the output circuit of the distorting device with its input circuit, said reentrant circuit having a plurality of paths each arranged to feed back ener corresponding to different even harmonics of the fundamental frequency, and means to prevent the feeding back of the energ of the fundamental frequency or odd iiarmonies thereof.

In testimony whereof, I have signed my name to this specification this 14th day of May 1923.

HERMAN A. AFFEL. 

